Effect of Parthenocarpic Genes pat-2 and pat-k on Vegetative and Fruit Traits in Tomato (Solanum lycopersicum 'Micro-Tom')

Parthenocarpy is a phenomenon that induces fruit set and development without pollination and fertilization. In tomato (Solanum lycopersicum L.) cultivation, parthenocarpy is considered to be an attractive trait, as it reduces the financial and labor costs involved in fruit set. Parthenocarpic genes pat-2 and pat-k are used as the source of parthenocarpic tomato cultivars in Japan. However, the effect of pat-2, pat-k, and their combined effect on vegetative and fruit traits are poorly understood, even though they are important for breeding parthenocarpic tomato cultivars. In this study, we introduced pat-2 and/or pat-k into a model tomato cultivar, `Micro-Tom', to compare their effects on one genetic background, and then examined their vegetative and fruit traits. Lines carrying pat-2 showed greater leaf and stem size and stomatal conductance compared with the wild-type (WT), whereas there was no significant difference in vegetative traits between a line carrying only pat-k (pat-k) and WT. In addition, the content of total soluble solids (TSS) in pollinated fruits of pat-k and the lines carrying pat-2 was higher and lower than that of WT, respectively. Although it is possible that genes linked to pat-2 or pat-k caused these effects, these results suggest that pat-2 and pat-k have pleiotropic effects on these vegetative and/or fruit traits. Moreover, the rate of fruit set of unpollinated fruits in a line carrying pat-2 and pat-k (pat-2/pat-k) was significantly higher than that in pat-k, and unpollinated fruits of pat-2/pat-k were significantly heavier than those of pat-k and a line carrying only pat-2, suggesting that the effects of pat-2 and pat-k on parthenocarpy are additive. The results of this study can be used as fundamental information for the breeding of parthenocarpic tomato cultivars using pat-2 and pat-k.